Aluminum alloys



Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE Aluminum Company ofAmerica, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing.

1 Claim.

This invention relates to aluminum base alloys containing magnesium. Theinvention has for its object the improvement of alloys of this class bythe addition thereto of about 0.05 to 2.0 per cent by weight of calcium.The invention is particularly concerned with the specific alloyshereinafter described.

The claim of this application covers certain matter divided from mycopending application Serial No. 634,155 which is, in part, acontinuation of my copending application Serial No. 595,231. Inventionsdisclosed but not claimed herein are claimed in my copending,applications Serial Nos. 595,231, filed February 25, 1932, 645,108 to645,121 inclusive, and 645,123 to 645,125 inclusive, all filed November30, 1932.

Considerable difficulty has heretofore been encountered in attempts tocommercially produce castings of aluminum base alloys containingsubstantial amounts of magnesium. This difilculty is encountered both inthe making of sand castings and permanent mold or chill-mold castings,although the nature of the difficulty difiers somewhat in each case. Inthe case of sand castings there occurs a reaction between the moltenaluminum base alloy containing magnesium and the ordinary sand-moldmaterials, or vapors generated therefrom. There is also a reaction withthe atmosphere. In addition, the magnesium-containing aluminum basealloy does not flow freely through narrow mold Sections at ordinarypouring temperatures and, if the pouring temperature be raised, thesolidified alloy is unsound. If the aluminum base alby containingmagnesium be cast in a chillmold the reaction effect is minimized tosome extent, but the troubles arising from cold-shuts and mis-runs areaccentuated because of the more rapidchilling of the molten metal. Theconsiderations apply to the aluminum base alloys specifically disclosedherein and particularly to such alloys. 1

I have discovered that when calcium is added to aluminum base alloys ofthe type and composition herein described, these difliculties are, to aconsiderable extent, eliminated. The calcium should be present inamounts ranging from 0.05 per cent to 2.0 per cent by weight subject tospecific considerations as hereinafter disclosed.

In the melting of aluminum alloys of the compositions herein described,a viscous scum often forms at the surface of the molten metal. Failureof the molten metal to run properly through narrow mold'apertures iscaused, in part, by shreds or particles of this scum'being suspended loyof relatively small amounts of calcium, in the Original applicationSeptember 21, 1932. Serial No. 634,155. plication November Divided andthis ap- 30, 1932. Serial No.

in the molten metal and offering a resistance to the free passage of themetal through the apertures. Regardless of the cause of this lowfluidity, I have discovered that the addition to the al- 0 preferredrange between 0.05 to 0.5 per cent, improves the casting characteristicsto a very considerable extent and simultaneously effects a reduction ofthe scum or dross collecting at or near the surface. In the casting ofarticles in sand molds, I prefer to add calcium in amounts less thanabout 0.5 per cent except in instances where some reduction of tensilestrength or other mechanical or tensile property is immaterial. Inamounts of more than 0.5 per cent the calcium addition produces theadvantages enumerated herein but has a tendency to lower some of .thephysical properties of the alloys. This efiect is not harmful whencalcium is present in amounts of about 0.5 per cent or less, but whenhigh strength is not a desideratum the. calcium may be used in amountsup to about 2.0 per cent. In intricate permanent mold castings, wherecasting troubles are very serious if no calcium be added, the improvedphysical properties obtained coincident with the production of goodcastings more than oifset the diminution in properties which mightotherwise result from the use of the calcium.

I have also discovered that when calcium is added to aluminum basealloys containing magnesium, the amount of gas evolved duringsolidification of the alloys is considerably reduced. When from about0.05 per cent to 2.0 per cent by weight of calcium is added to thealloys, the amount of gas evolved becomes less marked with increasingcalcium content and the reduction of gas evolution may be so marked thatthe molten metal cools to the solidification temperature with a smoothmirror-like surface. I prefer to restrict the amount of calcium added to2.0 per cent or less since above this amount the physical properties ofthe alloys may be too seriously affected. If the best physicalproperties are desired with an improved, although not complete, 100degree of gas prevention, I keep the calcium content of the alloysbetween 0.05 per cent and about 0.5 per cent.

In the application of the principles of my invention I have determinedthat certain alum- 105 inum base alloys containing magnesium areparticularly benefited thereby. For example, a very useful aluminum basealloy is one containing about 2.0 to 9.0 per cent of magnesium and 0.05per cent to 2.0 per cent of calcium, as is also 110 aluminum base alloycontaining about 2.0 to

15.0 per cent of magnesium, 0.1 to 3.5 per cent one of the class ofmetals here definedas antimony and bismuth, such alloys being veryuseful where use at high temperatures is contemplated. Calcium maylikewise be added to' improve such alloys when they contain, in additionto magnesium and antimony and/or bismuth, one or more of 'such alloyingelements as cobalt, copper, nickel, manganese, zinc, etc. which may beaddedvto modify or produce a specific property in the alloy.

cium is very beneficial in-the case of a series of aluminum base alloyswhich contain as major alloying elements about 2.0 to 10.0 per cent' ofmagnesium and about 0.2 to 5.0 per cent of nickel. For instance, analuminum base alloy containing 3.0 to 7.5 per cent of magnesium and 0.2to 2.0 per cent of nickel is improved by the addition of 0.05 to 2.0 percent of calcium as is, likewise, this same alloy when it also containsabout 0.05 to 0.4 per cent of one or more of the classof elementscomposed of antimony and bismuth. Another excellent aluminum base alloyprepared in accordance with the principles of my invention is onecontaining 3.0 to 8.0 per cent of magnesium, 0.5 to 4.0 per cent ofnickel, 0.5 to 4.0 per cent of manganese, and 0.05 to 2.0

per cent of calcium, which alloy may also be containing 2.0 to 10.0 percent of magnesium,

0.2 to 5.0 per cent of nickel, 0.5 to 3.5 per cent of chromium, and 0.05to 2.0 per cent of calcium. An aluminum base alloy containing 3.0 to 8.0per cent of magnesium, 0.5 to 3.5 per cent-of nickel, 0.5 to 3.5 percent of chromium, and 0.05 to 2.0 per cent of calcium has excellentcasting properties and the high temperature properties of this alloy canbe favorably affected by the addition of 0.05 to 0.4 per cent of atleast one of a class of elements composed of bismuth and antimony.Examples may be given of aluminum base alloy containing 2.0 to 10.0 percent of magnesium, 0.2 to 5.0 per cent of nickel, 1.0 to 6.0 per cent ofcopper, and 0.05 to 2.0 per cent of calcium. An excellent alloy of thistype is one containing 3.0 to 8.0 per cent of magnesium, 0.5 to 5.0 percent of nickel, 1.0

to-6.0 per cent of copper, and 0.05 to 2.0 per cent of calcium with orwithout 0.05 to 0.4 per cent of at least one of the class of elementscomposed of antimony and bismuth and with or without the furtheraddition of 0.5 to 3.5 per cent of at least one of a class of elementscomposed of cobalt and chromium, and with or without the furtheraddition of 0.1 to 1.0 per cent of at least one of a class of elementscomposed of tungsten, vanadium, molybdenum, titanium, and zirconium.

- Other excellent alloys are those aluminum base alloys containing about2.0 to 10.0 per cent magnesium, 0.2 to 5.0'per cent nickel, 0.1 to 3.5per The addition of 0.05 to 2.0 per cent of cal-' cent cobalt, and 0.05to 2.0 per cent of calcium. A particular example of this class ofalloys, which may also contain with considerable advantage 0.05to 0.4per cent of a class of elements composed of antimony and bismuth, is thealuminum base alloy containing 3.0 to 8.0 per cent magnesium, 0.5 to 4.0per cent nickel, 0.1 to 3.0 per cent cobalt, and 0.05 to 2.0 per centcalcium.

Among other magnesium-containing aluminum base alloys which I have foundto be particula'rly benefited by the presence of calcium are numberedthe aluminum base alloys containing 3.0'to 8.0 per cent" of magnesium,1.0 to 6.0 per cent of copper, 0.5 to 3.5 per cent of chromium, and 0.05to 2.0 per cent of calcium, with or without the addition of 0.05 to 0.4per cent of at least one of a class of metals composed of antimony andbismuth and with or without the addition of other alloying elements. V

The alloys herein described may be produced by the usual methods ofalloying metals. The calcium is preferably added to the molten alloy bythrusting the calcium beneath the surface with tongs or other suitableinstrument. The aluminum used in preparing the alloys may be pure' or itmay contain the impurities found in commercial gradesof this metal.Ordinarily a good commercial grade of virgin aluminum will giveexcellent results and is preferable.

Having thus explained and described my invention, I claim:

A metallic alloy consisting of 3.0 to 8.0 per cent by'weight ofmagnesium, 0.05 to 0.4 per cent by weight of at least one of a class ofelements composed of antimony and bismuth, 0.5 to 4.0 per cent by weightof nickel, 0.1 to 3.0 per cent by weight of cobalt, and 0.05 to 2.0 percent by weight of calcium, the balance being aluminum.

ROBERT T. WOOD.

